How to match subwoofers and amplifiers

Find the amp for your sub or the sub for your amp

The secret to great bass is making sure your subwoofers and amp are evenly matched and will properly work together. And this article will help you figure out how to do just that — match amplifiers and subwoofers. We cover the important basics of power-matching, impedance, and planning for the number of subs you want, and we approach the situation from both sides of the system:

Part A
You have the subs, which amp should you get?

The subs need to be the same
Multiple subs wired together must be the same coil type and impedance. If they’re not, the power won’t divide evenly between them, and some subs would probably be over-powered while others get under-powered. If you want to run different types of subs in a system, each type needs to have its own separate amp.

Step 1: How much power? Find out the “watts RMS” rating of the sub

Then, multiply the number of subs you have by the RMS rating of each, to get their total RMS rating. You want to make sure the amp you choose is capable of supplying from 75% to 150% of the sub system’s total RMS rating.

Step 2: What impedance? The results of combining coils and subs

Figure out the possible total impedance(s) that the subs can be wired together to form.
(SVC = single voice coil, 1 pair of terminals; DVC = dual voice coil, 2 pairs of terminals.)

Any one of these high-quality amplifiers would work well with those subs. It doesn’t matter which impedance an amp plays through — 600 watts RMS through a 4-ohm load produces the same volume as 600 watts RMS through a 1-ohm load. Notice that the Rockford Fosgate Power T1000-1bdCP can play that pair of subs at 700 watts RMS or 1,000 watts RMS, if you want it louder, just by wiring them together differently.

The last two amps listed above, the Focal 2300RX and the Rockford Fosgate Power T600-2, are 2-channel amps that happen to work with these two subs when bridged in 1-channel mode. But multi-channel amps are typically lower-powered than mono subwoofer amps, and usually can’t drive loads lower than 4 ohms when bridged.

Part B
You have the amp, which subs should you get?

Step 1: What can the amp do? Find the RMS ratings of the amp at different loads

Find the amp’s power, expressed in “watts RMS”, at 4 ohms, at 2 ohms, and, if it can, at 1 ohm. Pick the power you’d like to achieve. The load impedance (ohms) of that rating will be what you want your subs’ total impedance to be.

Step 2: How many subs do you want?

Divide the power you picked in Step 1 by the number of subs you want. This number is the target RMS rating for each of the subs you’ll choose.

Divide that target number by 1.5. This is the lowest RMS rating per sub that will work.

Divide that target number by 0.75 for the highest RMS rating per sub.

Step 3: What impedance does each sub need to be and how many voice coils?

Using the impedance you picked in Step 1 and the number of subs from Step 2, cross-reference the possible coil configurations that you can use:

1-ohm

2-ohms

4-ohms

1 sub

DVC 2-ohms

SVC 2-ohms
DVC 4 ohms

SVC 4-ohms
DVC 2-ohms

2 subs

SVC 2-ohms
DVC 4-ohms

SVC 4-ohms
DVC 2-ohms

SVC 2-ohms
DVC 4-ohms

3 subs

(1.3 ohms)*
SVC 4-ohms
DVC 2-ohms

(3 or 2.7 ohms)*
DVC 2-ohms
DVC 4-ohms

(6 ohms)*
SVC 2-ohms
DVC 4-ohms

4 subs

SVC 4-ohms
DVC 2-ohms

SVC 2-ohms
DVC 4 ohms

SVC 4-ohms
DVC 2-ohms

* Estimate amp power at the odd impedance values like in Part A, Step 3, above.

Step 4: Pick a sub that works for both — (SVC or DVC) X-ohms, Y watts RMS)

Look for subs that are rated within the wattage range you figured in Step 2, and are configured as you found in Step 3. This might sound confusing, so let's walk through an example and it'll make sense.

Let’s say you choose to maximize the amp’s potential and want the system to put out 500 watts RMS. This means your subs have to be wired to form a total impedance of 2 ohms.

Two subs on a 500 watts RMS amp will want about 250 watts RMS each.
250 divided by 1.5 is 167; 250 divided by 0.75 is 333. So you’ll look for subs each rated between 167 and 333 watts RMS.

Using the chart in Step 3, for two subwoofers, a final 2-ohm load can be achieved with either two SVC 4-ohm subs or two DVC 2-ohm subs.

So, you’ll look for two subs that are either SVC 4-ohms or DVC 2-ohms, rated between 167 and 333 watts RMS each:

2 SVC 4-ohms, (167-333) watts RMS, or

2 DVC 2-ohms, (167-333) watts RMS

Among Crutchfield’s selection of subwoofers you’ll find:

Kicker CompD 10"

JL Audio WXv2 Series 10" — SVC 4-ohm, 200 watts RMS

Infinity Reference Series 10" — SVC 4-ohm, 275 watts RMS

Kenwood Performance Series 10" — SVC 4-ohm, 300 watts RMS

Kicker CompD 10” — DVC 2-ohms, 300 watts RMS

Focal Performance 12” — SVC 4-ohm, 250 watts RMS

Pioneer Champion Series 12” — SVC 4-ohms, 300 watts RMS

Rockford Fosgate Punch P1 12” — SVC 4-ohms, 250 watts RMS

Kicker CompS 12” — SVC 4-ohm, 300 watts RMS

All these subwoofers will sound their best when amplified with the proper amount of power. Differences in size have more to do with tonal qualities and frequency response than with power performance. And optimizing performance is the point of matching subs and amps together.

Part C
If you have neither amp nor sub, and want help in deciding how to begin:

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Crutchfield Writer Biography

Buck Pomerantz

Buck Pomerantz was born and raised in Philadelphia. His parents bought their first television set when he was born. He figured out how to run it by the time he was two. Besides athletics, his formative interests included electronics, amateur radio, music, and stage crew work. He got his BA in writing from Brown University. Then he joined a rock 'n roll band as their soundman and moved to Charlottesville, Virginia. After that venture failed, he spent time in Boston, New Orleans, and Berkeley. He worked in a music store in Austin manufacturing, installing, repairing, and operating sound systems for recording studios, clubs, and bands. He moved back to Charlottesville, ran a little recording studio and finally joined Crutchfield as a copywriter. He has 2 grown children and 3 grandchildren, but after a good nap he can still rock out.